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.Dd September 17, 2011
.Dt DUPLOCALE 3
.Os
.Sh NAME
.Nm duplocale
.Nd duplicate an locale
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In locale.h
.Ft locale_t
.Fn duplocale "locale_t locale"
.Sh DESCRIPTION
Duplicates an existing
.Fa locale_t
returning a new
.Fa locale_t
that refers to the same locale values but has an independent internal state.
Various functions, such as
.Xr mblen 3
require a persistent state.
These functions formerly used static variables and calls to them from multiple
threads had undefined behavior.
They now use fields in the
.Fa locale_t
associated with the current thread by
.Xr uselocale 3 .
These calls are therefore only thread safe on threads with a unique per-thread
locale.
The locale returned by this call must be freed with
.Xr freelocale 3 .
.Sh SEE ALSO
.Xr freelocale 3 ,
.Xr localeconv 3 ,
.Xr newlocale 3 ,
.Xr querylocale 3 ,
.Xr uselocale 3 ,
.Xr xlocale 3
.Sh STANDARDS
This function conforms to
.St -p1003.1-2008 .
.Sh BUGS
Ideally,
.Xr uselocale 3
should make a copy of the
.Fa locale_t
implicitly to ensure thread safety,
and a copy of the global locale should be installed lazily on each thread.
The FreeBSD implementation does not do this,
for compatibility with Darwin.
